A festive collection of some of the best reads from the BBC's Science and Environment section this year.

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Sinkholes: A threat from the underworld. By Prof Iain Stewart

In February, Prof Iain Stewart explored the phenomenon of sinkholes, following the tragic death of a Florida man who was swallowed up by one of these natural trapdoors in 2013. Sinkholes are on the rise in Florida for a variety of reasons, including the weather, but also aggressive groundwater pumping for agriculture. Prof Stewart, who investigated the topic for a BBC Horizon documentary, wrote: "The lure of the Florida sun is drawing ever more people to the state, and our urban sprawl is advancing into wild land primed with lethal sinkhole traps. In the past, they would have gone unnoticed. But not now."

In March 1965, Alexei Leonov became the first person to walk in space. The mission was hailed as yet another triumph for the USSR over America against the backdrop of a battle for supremacy in space. But, as the 80-year-old Leonov told the BBC's Cosmonauts programme, this narrative bore little resemblance to what happened behind the scenes. Like a real-life version of the film Gravity, the mission was hit by a series of dire emergencies that left the crew fighting for their survival.

The BBC's science editor David Shukman visited a facility in China which produces an astonishing 500 cloned pigs a year. Because pigs have many genetic similarities to humans, they can serve as useful "models" for testing new medicines. The teams use established science, but the application of mass production is novel - and a further sign of China's rising ambition in the arena of science and innovation.

Could science help stop sharks attacking people in the ocean? As science writer Helen Scales says, humans kill millions more sharks than sharks kill people. But following a controversial cull in Western Australia, some scientists are looking at whether new approaches such as chemical repellents and novel wet suit designs could help deal with the issue.

BBC Horizon presenter Dr Michael Mosley investigated whether male and female brains really are wired differently. Research suggests that the connections in men and women's brains follow different patterns and scientists have proposed that this could explain typical forms of male and female behaviour. But big questions remain about whether these patterns are innate or if they are shaped by the world around us.

While covering the UN climate meeting in Lima, Peru, environment correspondent Matt McGrath visited the hillside settlement of Nuevo Pachacutec, where water is a prized commodity. Built in the desert, inhabitants pay 10% of their salaries for clean water delivered by a truck. But with storage methods posing a risk to health, some inhabitants are looking to other options for sourcing their supplies. Does the Peruvian community's experience give a glimpse of the future for many, as climate change places pressure on access to water?

Life today proceeds at breakneck pace. But in two famously lengthy experiments, scientists may wait up to a decade to observe pitch - the black muck left over from distilling crude oil - dropping from a funnel. A scientist who oversaw the best known experiment of this kind died without ever catching the pitch drip. Despite the curious nature of the research, these longest of long-term projects might help us understand how glass behaves and plan for the safe disposal of nuclear waste.

During the Ukraine crisis, tensions between Russia and the United States have reached a new peak. America responded to the crisis with tough sanctions, but in space, the countries are joined at the hip - dependent on one another for operating the International Space Station. The BBC's Rebecca Morelle examined whether the Ukraine tensions could spill into outer space.